▎ 摘　　要

A simple and scalable method has been developed for the synthesis of Co3O4-coated N-and B-doped graphene hollow spheres (Co3O4/NBGHSs). These Co3O4/NBGHSs are highly active for both oxygen reduction and evolution reactions and can exhibit higher electrocatalytic activities and better durability than commercial Pt/C and RuO2/C, respectively, demonstrating them to be efficient bi-functional electrocatalysts. In-depth analysis shows that the coupling between Co3O4 and NBGHSs, strong interaction with adsorbed O-2, high electric conductivity, and the specific hollow structure play important roles in imparting the higher electrocatalytic activities to the Co3O4/NBGHSs. When tested as cathode catalysts for Zn-air batteries, the Co3O4/NBGHSs exhibit better performance and higher stability than the Pt/C catalyst and other catalysts reported previously. This strongly suggests that the Co3O4/NBGHSs could be used as efficient electrocatalysts for metal-air batteries with great potential to replace precious metal/carbon based materials.